In this blog, we will discuss how to perform AC and thermal analyses using Q3D and Icepak. The thermal analysis will be performed using the electronic desktop Icepak. HFSS, 3D Layout, or Q3D can be used to generate power loss (dissipated) data for Icepak.
For the simulation of RLCG equivalent circuit of low frequency applications, Q3D is an extremely powerful and accurate tool. However, Q3D is limited in its ability to solve for high frequencies. HFSS is used for high frequency applications. The use of HFSS and Icepak is discussed in another blog.
| 3D Layout | Q3D | HFSS | SIwave | |
| Loss | DC Loss | AC Loss | RF Loss | DC Loss |
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Applications
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Multiple PCBs (Data Centers / Servers / )
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Power lines/ Bus bars (60Hz) Frequencies < 1 MHz or Small size (Dies)
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High power waveguides (Earth stations / Satellites / Radars) or High power amplifiers (Wireless Transmitters / Optical Modulators) or High power connector (Defense / airspace / wireless) or Biomedical Implants or Microwaves |
Single PCB
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| Icepack limitation | Full 3D | Full 3D | Full 3D | No access |
There are certain applications where a device needs to transmit a large amount of power through cables and bus bars. To build a proper cooling system around the power system, the designer needs to know the temperature.
Start by building your model, or import a one. Q3D, like HFSS, supports the import of STEP and SAT files in the standard MCAD format
Our model today is a busbar. The model carry 60Hz power signal of 5000Amp.
Start the Q3D setup. Initially, assign materials to all cables, say copper.
After that, assign source/sink to each bar. Unlike HFSS, Q3D ports do not need a reference. Each busbar (a net) needs at least one source and only one sink. Select the end surface of a net, right-click, elect Assign Excitations, Sink or Source. When you finish assign all the sources and sinks, go the Project Manager Panel, and right-click on the nets, and select Auto Identify Nets.
The next step is to add a solution setup:
There is no need to sweep. Due to the fact that thermal analysis is always performed at a single frequency point.
Change the amount of current running in each line. In the project Manager Panel, right-click the Field Overlays, and select Edit sources
The final step before starting the solution is to right-click on the model name and select to set the temperature, enable feedback for thermal analysis. Select all the components, and set the temperature to 20cel. Now the model is ready.
Press OK, and start solving.
Display the current on the surface of the cables.
In order to perform a thermal analysis, right-click on the name of the model and select Create Target Design. An Icepak model is created as a result.
Expand the Thermal section of the setup:
The model has two openings, opening 1 is simply an air flow opening.
The air is coming from Opening2. The air velocity is specified here.
When solving for temperature and flow, you will need these two Openings. You do not need them if you solve for the temperature alone. Take note of the air region surrounding the waveguide. Thermal analysis requires this information.
At this step, you can add any other component you want, like a fan, a heat spreader, other PCBs, enclosure, ...etc
Double-click the setup to verify it.
Select the discrete ordinates for the radiation. For the solver settings, change the air velocity to 0.1 to match the openings:
Start solving.
Check the loss numbers in the profile:
Certain faces have lots of loss, and others do not have any loss. This is because there is no current running on them.
After selecting all the busbars, right-click and select Plot Fields, Temperature, then Temperature.
Plot on surface,
The results are as follows:
The temperature distribution mtaches the current distribution that we saw in Q3D.
In the event that there are very high temperatures, due to a lossy design as in this case, the user may activate the two-way analysis. This can be accomplished by activating the two-way analysis in Thermal. Select Add 2-Way Coupling from the right click menu of the thermal model setup.
Press OK to set the number of iterations to 2,
In the Q3D model, right-click on the copper material and select properties to open the material panel. Click on the Edit material button:
In the View/Edit modifier for, select the Thermal Modifier option:
In other words, you are allowing the copper conductivity to change. The thermal formula for conductivity should be edited as follows:
The formula can be modified here in accordance with the supplier's instructions. In accordance with the default formula, the conductivity remains nominal if the temperature is between -25 and 1000 degrees Celsius. We change that to formula provided by google.
Once you have clicked OK, click OK again.
The setup for a two-coupling is now complete. Thermal analysis results are sent to Q3D, Q3D performs the analysis, and Icepak receives the results. The process is repeated two times.
1- Run Q3D again
2- Run Icepak
The new numbers are shown below.
